LEDs have several advantages over conventional filament or halogen bulbs. Since LEDs do not have a filament, the filament cannot burn out, which gives an LED longer life compared with both filament and halogen bulbs. However, LEDs generally emit less light than filament and halogen bulbs. To overcome this disadvantage, a type of LED lamp uses several individual low power LEDs to increase light output of the lamp.
It is desirable to use a single high-power LED in a lamp assembly rather than several low-power LEDs. However, an array of low-power LEDs generates a lower power density than lamp assemblies comprising a single high-power LED and so is easier to keep cool. A known type of lamp assembly comprising a single high-power LED comprises a metal housing in which the LED is mounted, the metal housing conducting the heat away from the LED. For heat-sinking configurations one may consult, for instance, US 2003/0040200 A1. “High-power” typically means ≧150 mA, “low-power” usually in the range 10-20, or say ≦50 mA.
It is also desirable to use high-power LEDs mounted in lamp assemblies that are formed from materials other than metal, such as glass, for decorative purposes. However, these materials do not conduct heat as well as metal, and can lead to the problem of heat building up near the LED, which can burn the LED out or in some cases lead to melting or fire. In general, the thermal properties of LED packaging are inadequately addressed in the prior art.